To obtain an image of an object, it is often necessary to scan the object by moving one of the object and the imaging system relative to the other. One common use in which this need arises is light microscopy, particularly where a tissue specimen is being imaged for diagnostic analysis; however, image scanning may be employed where there is no magnification, or where there is demagnification.
In microscopy, the need arises particularly when using conventional, single-axis, microscopes, where resolution must be traded off with the microscope's field of view (“FOV”) i.e., the FOV must be decreased in order to increase resolution. Therefore, a microscope with an objective having a FOV that is too small to image an entire specimen at a desired resolution is often provided with a motorized stage for scanning the specimen. The motorized stage translates microscope slides to, sequentially, move one portion of the specimen into a field of view of the microscope and then another, to obtain respective image portions of the specimen. An image of the entire specimen, or selected portions greater than the microscope's field of view, may be assembled from the individual two-dimensional fields of view in a process known as “tiling.”
This scanning is time-intensive. Moreover, the tiling process associated with this scanning exacts penalties in speed and reliability. Tiling requires computation overhead, and severe mechanical requirements are placed on the stage, e.g., to translate from one location to another accurately and to settle quickly for imaging, or tile alignment errors may be difficult or impossible to accurately correct. A most serious source of error results from differences in alignment between the line of sensors used for recording an image tile and the direction of horizontal slide transport provided by the scanning system.
Recently, a multi-axis imaging system has been developed employing an array of optical elements. Adapted for microscopy, the array is miniaturized to form a miniature microscope array (“microscope array”).
The microscope array is able to obtain a microscopic image of all, or a large portion, of a relatively large specimen or object, such as the 20 mm×50 mm object area of a standard 1″×3″ microscope slide. This is done by scanning the object line-by-line with an array of optical elements having associated arrays of detectors.
The optical elements are spaced a predetermined distance from one another, and the entire array and object are moved relative to one another so that the positional relationship between image data from the detectors is fixed, and data are thereby automatically aligned. This provides the outstanding advantage of eliminating the need for tiling.
Another outstanding advantage of the multi-axis imaging system is its speed. An entire specimen can be imaged in one pass because the FOV of the system can be arbitrarily large without sacrificing resolution. However, a mode of operation in which multiple passes are employed may still be needed where the dimensions of a given array are, for a given application, insufficient to cover the entire area of the object to be imaged in a single pass.
In complex scientific analysis, data from multiple sources are often combined to form a more complete perception of a phenomenon under observation. For example, in medical research, visual tissue information is combined with information about the presence or absence of certain chemical substances in the body of the tissue cells. The latter information may be obtained by use of fluorescent microscopy, two-photon microscopy, or multi-photon microscopy, to detect markers particular to the chemical compounds or biological structures under analysis. Researchers typically must use separate instruments to provide these different imaging modes of operation, which complicates data gathering and presents a problem of positionally correlating data from one instrument with the data from another.
Where conventional single-axis microscopes provide for multiple modes of operation, such as transmitted light and dark field illumination, the modes make use of common optical systems and cannot be used independently of one another, making positional correlation even more difficult as well as time consuming. Regarding multi-axis systems, while it is convenient using integrated manufacturing processes to fabricate arrays that realize a single imaging modality, it may not be practical or even possible to integrate manufacture of an array providing for a desired set of multiple imaging modalities.
Accordingly, there is a need for a multi-mode scanning imaging system that makes available the advantages of a multi-axis scanning imaging for multiple imaging modalities.